358 Harper: Native weeds and their probable origin 



Britain, New England, etc., as compared with more newly and 

 thinly settled regions of equal area and diversity. For in these old 

 countries few if any native species have yet been completely 

 exterminated, while the flora has been greatly augmented by the 

 species which seem to have been produced to meet the new condi- 

 tions of environment, to say nothing of introduced species, which 

 must have originated in a similar manner somewhere else. 



Furthermore, it will be noticed that the list given contains the 

 names of the genera which in the past decade or two have fur- 

 nished the most employment for species-makers in this part of the 

 world ; such as Achillea, Bidcns, Aster, Viola, Euphorbia, Oxalis, 

 Lespedesa, Chamaecrista, Rubus, Agrimonia, Polygonum, Sahx, 

 Sisyrinchium, Smilax, Jnncus, and Panicum. By analogy we may 

 expect some of the other genera to prove equally polymorphous 

 before long. European botanists have long been having similar 

 troubles with Hieraciwn, Crepis, Centaurea, Cirsium, Campanula, 

 Galium, Orobanche, Euphrasia, Euphorbia, Astragalus, Trifolium, 

 Rubus, * Rosa, Potentilla, Saxifraga, Ranunculus, Fumaria, Ery- 

 simum, Silene, Dianthus, Crocus, Car ex, \ Festuca, Poa, Avena, and 

 numerous other genera, and doubtless for similar reasons. 



Such plants as these, however interesting they may be to the 

 horticulturist, economic botanist, evolutionist, and laboratory 

 worker, have no place in a description of the natural or primeval 

 vegetation of the country, and their study can throw but little 

 light on the pre-historic development of the native flora, which is 

 one of the chief concerns of the phytogeographer. Their number 

 will probably continue to increase as long as the population of the 

 earth increases, and when they are described it would seem desir- 

 able to keep them by themselves, like cultivated plants, instead of 

 cumbering the pages of our manuals with them, to the confusion 

 and despair of the average botanist. In the present state of our 

 knowledge it may seem impossible to make a sharp distinction be- 

 tween native weeds and members of the original flora ; but authors 



*The perplexities of this genus in Europe are so great that English botanists W« 

 invented a special name, " batologists," for those who study it most. ^ 



t Carex, although one of our largest genera, has not furnished as many ' " 

 species" in the Eastern United States in the last fifty years as several formerly »u^ 

 smaller genera have. May this not be correlated with the fact that very fe wo1 ° 

 Carices are found in unnatural habitats? 



